Preparation of a MOF flame retardant containing phosphazene ring and its effect on the flame retardant of epoxy resin

With the aim of effectively improve the flame retardant and smoke suppression performance of epoxy resin (EP), a novel metal-organic framework (Zn-MOF) containing phosphazene ring and Zn2+ was synthesized by solicitation method. The results showed that adding 9 wt% solvent removed Zn-MOF (SR-Zn-MOF) could reduce the peak heat release rate (PHRR), the peak smoke production rate (PSPR), the peak of CO production (PCOP) and CO2 production (CO2P) of epoxy resin composites by 58.9, 45.8, 48.6, and 51.9%, respectively. Based on the analysis of the pyrolysis process of Zn-MOF and the study of the condensed phase char residues, it is found that the organic ligands containing phosphazene ring in Zn-MOF are thermally decomposed in the condensed phase to form the containing phosphoric acid and pyrophosphate substances, which together with the generated ZnO can effectively promote the carbonization of EP matrix. At the same time, the organic ligands will pyrolysis generate a large number of non-flammable gases such as NH3 and CO2, which can promote the intumescent of the char layer, and effectively dilute the concentration of combustible fuel and O2 in the gas phase. Therefore, Zn-MOF have excellent flame retardant and smoke suppression effect on EP.